1. Field of the Invention
This invention relates to an aspirating probe assembly useful in automated sample analysis and having a device associated therewith for washing the interior and exterior of the probe when the probe is not immersed in a liquid for aspitation thereof.
2. Prior Art
Heretofore, an aspirating probe has been associated with a sampler for the supply of a series of liquid samples for analysis seriatum. The samples may be a series of discrete blood serum specimens, each of which is supported and confined in a cup of a series of cups supported on a motor-driven turntable of the sample. The probe has been provided with a support for movement of the probe into the cup then indexed therewith for aspiration of the sample and then into the liquid within a stationary wash receptacle associated with the sampler for aspiration of wash liquid before the probe enters the next sample cup after movement of the turntable. Between immersions in sample and wash liquids, the probe has aspirated an immiscible fluid such as air and the resultant stream flowing from the probe has been segmented by segments of air and wash liquid, which segmentation of the sample stream preserves the integrity of the different samples. The segmentation is such that a wash liquid segment is located intermediate each sample and its neighbor and an air segment is located between each wash liquid segment and the adjoining sample as described in de Jong U.S. Pat. No. 3,134,263.
The probe assembly and sampler of Negersmith et al U.S. Pat. No. 3,266,322 accomplishes the same result described above but in a different way. In the latter, the stationary wash receptacle is disposed above the sample cup indexed with a probe which unlike the probe utilized in the de Jong disclosure has no angular movement on a verticle axis but has a similar up and down motion. The wash receptacle has vertically aligned openings above the sample cup indexed therewith, and the surface tension of the liquid within the receptacle is sufficient to prevent the wash solution from escaping through the small lower opening in the receptacle into the sample cup. As the probe leaves the sample cup, air is aspirated therein until the probe rises within the wash receptacle at which time the exterior of the probe is washed by the surrounding liquid and wash liquid is aspirated into the probe. Subsequently, the probe leaves the liquid in the wash receptacle in its upward movement and again aspirates air.
In Bannister et al U.S. Pat. No. 3,719,086, a stationary wash receptacle is provided over the indexed sample receptacle, such as is provided in Negersmith et al. The lower end of the aspirating probe is plugged and the probe has lateral inlet openings therein above the plug for the liquid which it aspirates such as a sample, and more specifically, the serum or plasma of a blood sample within a centrifuged sample cup. As in the Negersmith et al construction, the probe aspirates air in this case through the lateral inlets therein, on upward movement of the probe on leaving the sample receptacle to an intermediate postion of the probe. On further upward movement of the probe, the lower end of the probe is retracted to a position in which the plugged lower end lies below a flushing chamber in a bore formed in the receptacle and fluid is flushed through the chamber around an upper part of the probe and is aspirated from the chamber into the interior of the probe through the aforementioned inlet openings which are then disposed within the chamber. The plugged end of the probe within the aforementioned bore lies between the aforementioned chamber and a lower scavenging chamber from which fluid, mostly air, is sucked by a vacuum. It is pointed out by the patentees that there may be some flow of fluid from the chamber through the bore around the plugged section of the probe to the scavenging chamber. However, it appears that the bottom of the probe is not fully washed on the exterior thereof, and this may lead to contamination by the probe movements of one sample by another.
The aforementioned patents are believed to be typical of the prior art. It is proposed to overcome the difficulties with this prior art.